Of all the constructs created by Green Lantern, one manifestation simply puts Iron Man to shame. When Hal Jordan need to take on an entire army, he crafted a suit that Tony Stark could only dream of.
Even among the brilliant minds of the Marvel Universe, there are few people capable of creating a weapon like Stark's signature line of armors. Since his very first oversized suit, the genius has only gotten better at improving on his Iron Man armor, adding new, cutting-edge tech to make him one of the most capable heroes in the Marvel world. While Iron Man has created some pretty cool weapons, it doesn't take a genius to operate a Green Lantern's Power Ring, which is able to generate anything anyone can think up. Instead of technical know-how, all one needs is just a spark of imagination to bring their wildest visions to life. While Green Lantern created his own Iron Man suit in a non-canon crossover, he also made one in the main DC Universe.
Case in point, Hal Jordan, one of the DCU's premier ring-slingers, showed off his uncanny abilities to bring wild and fantastic ideas into reality. In Green Lantern #14 by Geoff Johns and Ivan Reis, Hal is still adjusting to reality after the last year of his life in the wake of Infinite Crisis. During the events of "One Year Later" Hal and several of his friends were taken hostage by a terrorist group and held for months. Though they escaped, the government drafts Hal's love interest and fellow POW Jillian "Cowgirl" Perlman into a mission to take out the terrorist cell. Unfortunately, Perlman's plane goes down overseas and Hal knows it will take too long for the Air Force to launch a proper rescue. Lighting up his Power Battery, Hal Jordan returns to his former prison to rescue Jillian, clad in an armor constructed from his ring.
The construct made by Green Lantern is only temporary and as soon as Jordan touches down on the camp, he uses his ring in a manner much more suited to the hero. But his suit is quite impressive in the brief time its seen. Hal might not be familiar with the intricacies of how to design a non-construct version of such an armor, but thankfully his ring can do the heavy lifting for that, something that may give him an edge over the mind of Tony Stark.
No one can seriously say that Tony hasn’t made some seriously powerful armors in his time as Iron Man, but he's unfortunately stymied by whatever technological limitations he runs into. Even the most advanced tech can only go so far. But with a Green Lantern's Power Ring, there is no such limitation, except one's imagination. Hal has nowhere near the brainpower to build a fully functioning set of armor like Tony, but with a ring, he can certainly visualize one. If Tony Stark could get his hands on a ring like that, he'd likely build something beyond his wildest dreams. But for now, Iron Man is just going to have to accept his armor is limited in a way the Green Lanterns are not.